The present invention relates to a method for removing an unnecessary substance from a silicon substrate surface.
In the prior art as shown in FIG. 2, an unnecessary SiOx (Silicon oxide) film 22 and an unnecessary CHx (hydrocarbon) film 23 on a Si (Silicon) substrate 21 are heated to a temperature not less than 750.degree. C. in vacuum circumstances with a pressure not larger than 10.sup.-7 Pa so that the SiOx film 22 is changed to SiO to be removed from the Si substrate 21 and H (hydrogen) of the CHx film 23 is removed therefrom. But at least a part of C (carbon) of the CHx (hydrocarbon) film 23 remains on the Si substrate 21 and a SiCx compound is formed.
Subsequently, in order to form an ultra-clean surface composed of planar terraces 31 and steps 33 on a cleaned Si substrate 31 a shown in FIG. 3, the SiCx compound including the remaining C is removed from the Si substrate 21 by being heated to a temperature not less than 1100.degree. C., alternatively, as shown in FIG. 4, the remaining C is removed from a Si substrate 36 by being exposed to ozone which is generated by applying ultraviolet rays to O.sub.2 gas.